Question

Differentiate physisorption and chemisorption.

Answer 1

Sr. No.	Chemisorption	Physisorption
1.	It is very slow.	It is instantaneous.
2.	It is very specific depends on nature of adsorbent and adsorbate.	It is non-specific.
3.	Chemical adsorption is fast with increase pressure, it can not alter the amount.	In Physisorption, when pressure increases the extent of adsorption increases.
4.	When temperature is raised chemisorption first increases and then decreases.	Physisorption decreases with increase in temperature.
5.	Chemisorption involves transfer of electrons between the adsorbent and adsorbate.	No transfer of electrons
6.	Heat of adsorption is high i.e., from 40-400 kJ/mole.	Heat of adsorption is low in the order of 40 kJ/mole.
7.	Monolayer of the adsorbate is formed.	Multilayer of the adsorbate is formed on the adsorbent.
8.	Adsorption occurs at fixed sites called active centres. It depends on surface area.	It occurs on all sides.
9.	Chemisorption involves the formation of activated complex with appreciable activation energy.	Activation energy is insignificant.